As one type of wiring substrates used for semiconductor packages, coreless substrates that do not include core substrates are known. Coreless substrates are suitable for reducing the thickness of the wiring substrates. Conversely, because a coreless substrate more easily deflects than a wiring substrate including a core substrate and does not easily maintain its shape, the coreless substrate is not easily handled. Accordingly, a coreless substrate may be bonded to a stiff carrier and then a semiconductor chip may be mounted. Adhesion to the carrier enhances handling of the core substrate.